At the beginning of the second season Sergeant Voight tries to find out who is behind the murder of Jin, and come up with the unbelievable discovery and learned that Sergeant Edwin Stillwell playing a double game with the intention of getting out on the surface of the big fish along with Voight. In the meantime, all members of the intelligence departments receive death threats from an unknown group called “Shadow”. At several places in Chicago in a fire, explosion, and robbery, for which “Shadow” take responsibility, bringing the city into chaos.